1. Field of the Invention
The present invention relates to a torque detecting apparatus applicable to an electromotive bicycle fitted with a motor as an auxiliary drive source for example. The torque detecting apparatus of the present invention detects torque by way of transmitting drive force via a pair of rotary bodies that cause own relative position to be varied by effect of torque, to enable detection of variation of resonant frequency corresponding to variation of relative position under non-contact condition or to enable transmission of modulated signal corresponding to variation of the relative position under non-contact condition, whereby enabling the apparatus to correctly detect actual torque based on a simple structure with high precision.
2. Description of Related Art
Any of conventional electromotive bicycles has been so arranged that drive of the drive wheel can be assisted by motor-drive force in correspondence with operation of pedals performed by user within such a scope that does not affect operating safety.
Concretely, in such a conventional electromotive bicycle, ratio between pedaling force of user and drive force of the motor is designated by assist ratio. Practically, it is so arranged that the assist ratio can remain at 1:1 within such a range in which the bicycle runs at a relatively slow speed up to 15 km/h. On the other hand, it is so arranged that the assist ratio can gradually be decreased from 1:1 to 1:0 in correspondence with actual speed within a scope from 15 km/h to 25 km/h.
Because of the above arrangement, a variety of torque detecting mechanisms have been provided for conventional electromotive bicycles to detect actual pedaling force generated by users to cause the motor to be driven based on the result of the detected pedaling force.
For example, FIG. 29 is a lateral view showing such a torque detecting mechanism and the torque detecting device 1 which causes a planetary gear 2 to transmit pedaling force to detect actual pedaling force by way of detecting torque counter-force generated on the part of a stationary gear 3.
In specific, as shown in a partially enlarged portion with arrow A, the torque detecting device 1 has such a structure in which the stationary gear 3 having teeth being formed along external circumference is secured to a stationary portion 4. The stationary gear 3 is secured to the stationary portion 4 by effect of a compressed spring 5 disposed between a projected piece 3A projecting itself inside of the stationary gear 3 and another projected piece 4A projecting itself on the part of external circumference of the stationary portion 4.
The planetary gear 2 is rotatably retained by an annular member 6, where the planetary gear 2 is disposed by way of engaging own teeth with the stationary gear 3 across approximately 120 degrees of angular interval on the part of external circumference of the stationary gear 3. In the above-cited torque detecting device 1, a crank is connected to the annular member 6. Motor drive force is transmitted via a further transmission mechanism which is not shown in the drawing.
In the torque detecting device 1, a drive gear 8 is disposed by way of surrounding the planetary gear 2. Teeth formed on the part of internal circumference of the drive gear 8 are disposed via engagement with teeth of the planetary gear 8. In the torque detecting device 1, the drive gear 8 is rotated by drive force transmitted to the planetary gear 2 via the crank whereby transmitting drive force further to a chain 9 being engaged along external circumference of the drive gear 8.
When drive force is transmitted in this way, by way of resisting pressing force of the compressed spring 5 after being affected by counter force of torque, as shown via arrow B, the stationary gear 3 displaces itself in correspondence with actual magnitude of torque. In response, the torque detecting device 1 causes torque to be converted into displaced amount of the stationary gear 3, where the torque is variable in correspondence with actual pedaling force.
The torque detecting device 1 converts the displaced amount into electrical signal via a variable resistor or the like secured to the stationary portion 4, and then, after processing electrical signal, pedaling force of user can be assisted with motor drive force solely in such a case in which user actually operates pedals with own pedaling force.
FIG. 30 is a plan view showing another example of a conventional torque detecting device 11, in which drive force is sequentially transmitted via a coaxially supported torque converter 13 and a drive-force transmitting rotary body 12. The torque converter 13 transmits drive force to the drive-force-transmitting rotary body 12 via an elastic member such as a spring elongating and contracting itself to subsequently cause relative position of a pair of rotary bodies 12 and 13 to be variable in correspondence with drive force.
In the torque converter 13, it is so arranged that projecting amount of a drive-force transmitting pin 14 can be varied by the variation of the relative position of the above two rotary bodies, and yet, as is designated by reference code C, it is so arranged that a receptive plate 15 rotatably being held by a shaft can be displaced by the drive-force transmitting pin 14. In the torque detecting device 11, it is so arranged that the receptive plate 15 can be energized by a spring 17 secured to a stationary body 16, and yet, by way of expanding displaced amount of the receptive plate 15 by applying a lever 18, the displaced amount is transmitted to another torque detecting device 19. For example, the torque detecting device 19 comprises a variable resistor whose resistance value is variable in correspondence with the displaced amount transmitted via the lever 18. According to the above arrangement, the torque detecting device 11 transmits any variation on the rotary bodies corresponding to actual torque to the stationary members, and then, after properly processing electrical signal transmitted from the variable resistor, the torque detecting device 11 detects drive torque.
FIGS. 31A and 31B are a plan view and a lateral view of a still further example of the conventional torque detecting device. A torque detecting device 21 incorporates a first rotary body 22 and a second rotary body 23 which are respectively disposed via coaxial structure. The first rotary body 22 is rotated by the pedaling force of user, whereas the second rotary body 23 is engaged with a chain 24. The first rotary body 22 and the second rotary body 23 respectively transmit drive force via an elastic member such as a spring to cause relative position to be variable in correspondence with actual pedaling force.
Further, a window 22A and another window 23A are individually provided for the first rotary body 22 and the second rotary body 23 so that they superpose with each other. Whenever the relative positions of the first and second rotary bodies 22 and 23 are shifted, it is so arranged that dimension of aperture formed by the windows 22A and 23A can be varied as well.
A light-emitting unit 26 and a light-receiving unit 27 are secured to the torque detecting device 21 so as to sandwich the aperture. By causing the light-receiving unit 27 to detect measuring light emitted from the light-emitting unit 26, the torque detecting device 21 detects such a torque-detect signal comprising a certain duty ratio being subject to variation in correspondence with actual pedaling force generated by user, as shown in FIG. 32.
Nevertheless, in such a conventional structure using a planetary gear as was described earlier by referring to FIG. 29, it is quite essential that structure in the periphery of the stationary gear be strong enough to withstand pedaling force and drive force, whereby entailing complex structure, and yet, increasing weight. Further, it also entails problem in that operating efficiency remains low, and yet, the structure may require generation of useless force.
On the other hand, in such a system that mechanically detects variation of the relative position of the two rotary bodies as was described earlier by referring to FIG. 30, compared to the case of utilizing a planetary gear, overall structure can be simplified, and yet, generation of noise can be suppressed. Nevertheless, when utilizing this system in order to mechanically transmit the result of pedaling force detected on the movable side, it is essential that the receiving plate 15 be finely fabricated with precision. This in turn entails the complex structure, thus raising problem as well. Further, quality degradation during the service term caused by the wear between the rotary bodies and the stationary body also raises another problem.
On the other hand, in such a system that optically detects variation of the relative position of a pair of rotary bodies as was described above by referring to FIG. 31, it is possible to detect the result of computing pedaling force detected via variation of relative position of the two rotary bodies under non-contact condition, and thus, problems arising from the above-referred two system can be solved. However, when utilizing the optical detection system, torque is intermittently detected, and thus, in order to reduce such a period entailing difficulty to detect torque, it is essential that the number of aperture be increased. Further, in order to improve detecting precision, it is also necessary to enhance precision for forming apertures, whereby causing the processing work to entail complexity to raise another problem.
Aside from the above systems, such a method for detecting pedaling force by way of checking loosened amount of the chain has also been proposed. However, none of the above-referred torque detecting systems has ever been proven to be practically sufficient.
The present invention has been achieved to fully solve the above problems by way of providing a novel torque detecting apparatus capable of correctly detecting actual torque with a simple structure and high precision.
In order to solve the above problems, the present invention according to claim 1 comprises the following:
displacement detecting means for generating torque modulated signal which is modulated by torque signal corresponding to variation of relative position between a rotary body disposed on the part of drive source being variable in correspondence with torque and another rotary body disposed on the output side; and
signal transmitting means for transmitting torque modulated signal from the drive-source-side rotary body to a stationary member or from the output-side rotary body to a stationary member under non-contact condition.
According to the structure according to claim 1, a novel torque detecting apparatus comprises a displacement detecting means for generating torque-modulated signal which is modulated by torque signal corresponding to variation of relative position between a rotary body disposed on the part of drive source being variable in correspondence with torque and another rotary body disposed on the output side and a signal transmitting means for transmitting torque-modulated signal from the drive-source-side rotary body to a stationary member or from the output-side rotary body to a stationary member under non-contact condition. Because of the above arrangement, it is possible for the stationary side to detect torque by way of demodulating the torque-modulated signal under non-contact condition, whereby enabling prevention of precision from incurring degradation otherwise caused by the wear of the components to eventually make it possible to correctly detect actual torque with high precision with a simple structure.